Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 2,383	$ 1,819	$ (652)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(483)	103	(94)
Realized and unrealized gains (losses) on derivatives	(29)	(14)	9
Realized and unrealized gains (losses) on marketable securities	4	5	(1)
Pension and postretirement plans	0	0	(1)
Other comprehensive income (loss)	(508)	94	(87)
Total comprehensive income (loss)	1,875	1,913	(739)
Comprehensive income attributable to noncontrolling interests	186	203	225
Comprehensive income (loss) attributable to Johnson Controls	$ 1,689	$ 1,710	$ (964)